By Shayne Chun, Webcor Senior Project Engineer

The New Hospital at UCSF Helen Diller Medical Center at Parnassus Heights (NHPH) is being developed in a collaborative culture with a team of designers, builders, and the client through an Integrated Form Of Agreement (IFOA) approach. The Herrero Boldt Webcor (HBW), a tri-venture partnership between Herrero Builders, Inc., The Boldt Company, and Webcor, is the general contractor partner for the NHPH. The Site Make Ready (SMR) projects consist of over 20 projects, in addition to the new hospital, which range from $400,000 to $20 million.

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For this update, we would like to highlight our SMR 1 deep sewer relocation project that utilizes a jack and bore operation (a trenchless method of underground utility construction) for the sewer installation. This project relocates a main sewer line that runs through the future hospital site.  It is a particularly challenging project, as it’s up to 30 feet deep on an active road and next to an active hospital.

To execute this work, the team had to use the jack and bore. This jack and bore method utilizes an auger bore machine, steering heads, a crane, welding machines/generators, and a bentonite pump to install 36"x10' steel casings for 18-inch Combined Sewer and Sanitary (CSS) installation on Medical Center Way.

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The jack and bore method for sewer construction commences with the excavation and shoring of a launch pit and receiving pit to the required depths. For this particular jack and bore operation, the launch pit is 29 feet deep and the receiving pit is 27 feet deep. With the completion of the excavation and installation of the slide rail shoring system, the ground in the launch pit gets leveled to set the auger bore machine rail.

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Next, the auger bore machine gets hoisted down into the launch pit. The actual jack and bore operation begins by drilling a hole horizontally to place the steel casings at the bottom of the launch pit to the receiving pit. Once the casing is jacked in place, the augers are removed from inside the casing tunnel. The pressure grout operation follows next to secure the steel casing in place.

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When the casings are in place and secured, the 18-inch PVC CSS is installed through the steel casings to the receiving pit from the launch pit. The pictures above demonstrate the installation of the 18-inch PVC CSS in the launch pit to the receiving pit on Medical Center Way.

The jack and bore operation for the CSS installation on Medical Center Way is certainly challenging with unforeseen conditions under the ground, but it’s also a unique way of installing the CSS line when it cannot be trenched.